The present invention relates to valves for regulating fluid flow.
Ball valves are known in the art, and have traditionally been used as an effective mechanism for regulating fluid flow in conduits. They are commonly found in plumbing for the home, recreational vehicles, mobile homes, garden, or general landscaping. Various structural arrangements have been achieved for interrupting fluid flow by twisting a handle of a ball valve, and resuming fluid flow by twisting the handle back again. Typically, ball valves include a housing having an inlet port and an outlet port. A throughbore internally connects the inlet port to the outlet port. An inlet conduit and an outlet conduit may be connected to the inlet port and the outlet port respectively. A central chamber is positioned in the path of the throughbore. A ball with a throughbore is positioned within the central chamber. The ball may be rotated by an external handle. When the handle is twisted to align the throughbore of the ball with the path of the throughbore, the throughbore is uninterrupted and fluid may flow between the inlet and outlet ports. When the handle is twisted so that the slot lies perpendicular to the throughbore, fluid flow is interrupted.
In a particular aspect of the prior art, found in U.S. Pat. No. 5,308,039 (King) which is concurrently owned by the applicant, the ball may be caused to “expand” as it is rotated towards the closed position. This expansion is caused by a camming surface strategically positioned to expand the ball upon rotation of the ball. In this prior art, the camming surface is symmetrical about an axis that extends parallel with the axis of the throughbore and the surface causes the ball to continually expand as the handle is turned from its open position to its closed position. Thus, as the ball is twisted toward the closed position, the force required to close the valve steadily increases until the ball has reached its fully closed position. This aspect of the prior art is more fully discussed below with reference to FIGS. 3 and 7.
However, disadvantages are found to exist in the prior art. First, it has been found that water pressure in the conduit line is capable of cracking the seal between the ball and the chamber, causing the ball to start rotating toward the open position. The possibility of this disadvantageous outcome may be exacerbated if a vibration is imposed on the closed valve, which would tend to reduce the frictional resistance that otherwise restrains the ball from moving away from its closed position. Second, it has been found that the presence of salt or sediment deposits in the valve housing and/or on the ball surface may tend to obstruct the ball from reaching its fully closed position.
Thus, there is a need for a ball valve that overcomes the above. The present invention addresses these and other needs.